Neurobehavioral toxicity study of dibutyl phthalate on rats following in utero and lactational exposure

The combined neurotoxicity of DBP and nano-TiO2 in embryonic zebrafish (Danio rerio) revealed by oxidative activity, neuro-development genes expression and metabolomics changes

Dibutyl phthalate (DBP) is a commonly used plasticizer that is frequently detected in water samples due to its widespread use. Titanium dioxide nanoparticles (n-TiO2) have been found to enhance the harmful effects of organic contaminants by increasing their bioavailability in aquatic environments. However, the combined toxic effects of DBP and n-TiO2 on aquatic organisms remain unclear. This study aimed to investigate the neurotoxicity of DBP and n-TiO2 synergistic exposure during the early life stage of zebrafish. The results of the study revealed that co-exposure of DBP and n-TiO2 led to an increase in deformities and a significant reduction in the active duration of zebrafish larvae. Furthermore, the co-exposure of DBP and n-TiO2 resulted in elevated levels of oxidative stress and altered gene expression related to neurodevelopment and apoptosis. Notably, n-TiO2 exacerbated the oxidative damage and apoptosis induced by DBP alone exposure. Additionally, co-exposure of the 1.0 mg/L DBP and n-TiO2 significantly affected the expression of genes associated with neurodevelopment. Moreover, disturbances in amino acid metabolism and interference with lipid metabolism were observed as a result of DBP and n-TiO2 co-exposure. In general, n-TiO2 aggravated the neurotoxicity of DBP in the early life stage of zebrafish by increasing oxidative stress, apoptosis, and disrupting amino acid synthesis and lipid metabolism. Therefore, it is essential to consider the potential risks caused by DBP and nanomaterials co-existence in the aquatic environment.

Prenatal Di-methoxyethyl phthalate exposure impairs cortical neurogenesis and synaptic activity in the mice

Di-methoxyethyl phthalate (DMEP) is a well-known environmentally prevalent endocrine disruptor and may be associated with neurodevelopmental disorders including attention deficit/hyperactivity disorder and intellectual disability. However, the regulatory mechanisms leading to these neurodevelopmental disorders are still poorly understood. Here, we demonstrate that prenatal DMEP exposure causes abnormal brain morphology and function in the mice. DMEP (50 mg/kg) was chronically administered to pregnant mice orally once a day starting on embryonic day 0 (E0) to breast-feeding cessation for the fetus. We found that prenatal DMEP exposure significantly reduced the number of neurons in the parietal cortex by impairing neurogenesis and gliogenesis during the developing cortex. Moreover, we found that prenatal DMEP exposure impaired dendritic spine architectures and synaptic activity in the parietal cortex. Finally, prenatal DMEP exposure in mice induces hyperactivity and reduces anxiety behaviors. Altogether, our study demonstrates that prenatal DMEP exposure leads to abnormal behaviors via impairment of neurogenesis and synaptic activity.

What risk factors for Developmental Language Disorder can tell us about the neurobiological mechanisms of language development

Language is a complex multidimensional cognitive system that is connected to many neurocognitive capacities. The development of language is therefore strongly intertwined with the development of these capacities and their neurobiological substrates. Consequently, language problems, for example those of children with Developmental Language Disorder (DLD), are explained by a variety of etiological pathways and each of these pathways will be associated with specific risk factors. In this review, we attempt to link previously described factors that may interfere with language development to putative underlying neurobiological mechanisms of language development, hoping to uncover openings for future therapeutical approaches or interventions that can help children to optimally develop their language skills.

Sex-specific Effects of Endocrine-disrupting Chemicals on Brain Monoamines and Cognitive Behavior

The period of brain sexual differentiation is characterized by the development of hormone-sensitive neural circuits that govern the subsequent presentation of sexually dimorphic behavior in adulthood. Perturbations of hormones by endocrine-disrupting chemicals (EDCs) during this developmental period interfere with an organism's endocrine function and can disrupt the normative organization of male- or female-typical neural circuitry. This is well characterized for reproductive and social behaviors and their underlying circuitry in the hypothalamus and other limbic regions of the brain; however, cognitive behaviors are also sexually dimorphic, with their underlying neural circuitry potentially vulnerable to EDC exposure during critical periods of brain development. This review provides recent evidence for sex-specific changes to the brain's monoaminergic systems (dopamine, serotonin, norepinephrine) after developmental EDC exposure and relates these outcomes to sex differences in cognition such as affective, attentional, and learning/memory behaviors.

Phthalate Exposure, PPARα Variants, and Neurocognitive Development of Children at Two Years

Background: The PPARα gene may be crucial to the neurotoxic effect of phthalates. However, epidemiological studies considering the neurodevelopmental influence of phthalates interacting with genetic susceptibility are limited. We hypothesized phthalates could interact with the PPARα gene, synergistically affecting neurocognitive development.

Methods: A total of 961 mother-infant pairs were involved in this study. The concentrations of phthalate metabolites in maternal urine during pregnancy were detected. Children’s neurocognitive development was estimated with the Bailey Infant Development Inventory (BSID). Genetic variations in PPARα were genotyped with the Illumina Asian Screening Array. We applied generalized linear regression models to estimate genotypes and phthalate metabolites’ association with children’s neurocognitive development.

Results: After adjusting for potential confounders, the mono-n-butyl phthalate (MnBP) concentration was negatively associated with Psychomotor Development Index (PDI) (β = −0.86, 95% CI: −1.67, −0.04). The associations between MnBP and neurocognitive development might be modified by PPARα rs1800246. Compared with low-MnBP individuals carrying rs1800246 GG genotypes, high-MnBP individuals with the AG + AA genotype had a higher risk of neurocognitive developmental delay, with the odds ratio of 2.76 (95% CI:1.14, 6.24).

Conclusions: Our current study revealed that prenatal exposure to MnBP was negatively correlated with children’s neurocognitive development, and PPARα rs1800246 might modify the association.

Behavioral Effects of Exposure to Phthalates in Female Rodents: Evidence for Endocrine Disruption?

Phthalates have been widely studied for their reprotoxic effects in male rodents and in particular on testosterone production, for which reference doses were established. The female rodent brain can also represent a target for exposure to these environmental endocrine disruptors. Indeed, a large range of behaviors including reproductive behaviors, mood-related behaviors, and learning and memory are regulated by sex steroid hormones. Here we review the experimental studies addressing the effects and mechanisms of phthalate exposure on these behaviors in female rodents, paying particular attention to the experimental conditions (period of exposure, doses, estrous stage of analyses etc.). The objective of this review is to provide a clear picture of the consistent effects that can occur in female rodents and the gaps that still need to be filled in terms of effects and mode(s) of action for a better risk assessment for human health.

Prenatal exposure to phthalates and its effects upon cognitive and motor functions: A systematic review

Phthalates are chemicals widely used in packaging and consumer products, which have been shown to interfere with normal hormonal function and development in some human and animal studies. In recent decades, pregnant women's exposure to phthalates has been shown to alter the cognitive outcomes of their babies, and some studies have found delays in motor development.

METHODS

electronic databases including PubMed/MEDLINE and Scopus were searched from their inception to March 2021, using the keywords "phthalate", "cognitive" and "motor".

RESULTS

most studies find statistically significant inverse relationships between maternal urinary phthalate concentration during pregnancy and subsequent outcomes in children's cognitive and motor scales, especially in boys rather than girls. However, many associations are not significant, and there were even positive associations, especially in the third trimester.

CONCLUSION

the relationship between exposure to phthalates during pregnancy and low results on neurocognitive scales is sufficiently clear to adopt policies to reduce exposure. Further studies are needed to analyze sex differences, coordination and motor scales, and phthalate levels during breastfeeding.

Nimodipine attenuates dibutyl phthalate-induced learning and memory impairment in kun ming mice: An in vivo study based on bioinformatics analysis

Dibutyl phthalate (DBP), a typical representative of phthalate esters (PAEs), is used as a plasticizer in various industrial applications and has been reported to be responsible for neurobehavioral changes. Despite mounting evidence showing that nimodipine (Nim) palys a neuropharmacological and psychopharmacological role in neurons, the attenuating effects of Nim on learning and memory impairment induced by DBP exposure remain unknown. Based on bioinformatics analysis we found that the biological processes affected by both DBP and Nim may involve the calcium signaling pathway, the MAPK signaling pathway and the apoptosis pathway. The results of an in vivo study confirmed that DBP affects the levels of Ca²⁺ -related proteins, up-regulates phosphorylated -ERK1/2 expression and results in hippocampal neuronal damage and apoptosis, whereas Nim as a Ca²⁺ antagonist, has a certain neuroprotective role to avoid these adverse effects. Our data suggest that Nim could be used to attenuate the learning and memory impairment in DBP-exposed mice, to down-regulate intracellular Ca²⁺ levels, subordinate the ERK1/2 pathway and attenuate apoptosis in hippocampal tissue.

Maternal Exposure to Dibutyl Phthalate (DBP) or Diethylstilbestrol (DES) Leads to Long-Term Changes in Hypothalamic Gene Expression and Sexual Behavior

Xenobiotic exposure during pregnancy and lactation has been linked to perinatal changes in male reproductive outcomes and other endocrine parameters. This pilot study wished to assess whether brief maternal exposure of rats to xenobiotics dibutyl phthalate (DBP) or diethylstilbestrol (DES) might also cause long-term changes in hypothalamic gene expression or in reproductive behavior of the resulting offspring. Time-mated female Sprague Dawley rats were given either DBP (500 mg/kg body weight, every second day from GD14.5 to PND6), DES (125 µg/kg body weight at GD14.5 and GD16.5 only), or vehicle (n = 8–12 per group) and mild endocrine disruption was confirmed by monitoring postnatal anogenital distance. Hypothalamic RNA from male and female offspring at PND10, PND24 and PND90 was analyzed by qRT-PCR for expression of aromatase, oxytocin, vasopressin, ER-alpha, ER-beta, kisspeptin, and GnRH genes. Reproductive behavior was monitored in male and female offspring from PND60 to PND90. Particularly, DES treatment led to significant changes in hypothalamic gene expression, which for the oxytocin gene was still evident at PND90, as well as in sexual behavior. In conclusion, maternal xenobiotic exposure may not only alter endocrine systems in offspring but, by impacting on brain development at a critical time, can have long-term effects on male or female sexual behavior.

Temporal Trends of Exposure to Phthalates and Phthalate Alternatives in California Pregnant Women during 2007-2013: Comparison with Other Populations

Phthalates with potential adverse health effects are being replaced by other phthalates or phthalate alternatives. Little is known about temporal trends of phthalate exposure in pregnant women in the United States. We quantified 16 metabolites of eight phthalates and di(isononyl) cyclohexane-1,2-dicarboxylate (DINCH) in 656 urine samples collected from 192 California pregnant women in 2007-2013 during their second and third trimesters of pregnancy who participated in the MARBLES (Markers of Autism Risk in Babies-Learning Early Signs) study. We used multiple regression to estimate least squares geometric means of phthalate biomarker concentrations and annual percent changes over the study period. Biomarker concentrations of diethyl phthalate (DEP) and three phthalates with known toxicity and adverse health effects (i.e., butyl benzyl phthalate [BBzP], dibutyl phthalate [DBP], di(2-ethylhexyl) phthalate [DEHP]) decreased, while those of di-isobutyl phthalate [DiBP], di-isononyl phthalate [DiNP], and di-n-octyl phthalate [DOP] increased in California pregnant women during our study period. To understand broad social forces that may influence temporal trends and geographic variations in phthalate exposure across countries, we compared our phthalate biomarker concentrations with those of other populations. We observed over a factor of 2 differences in exposure across countries for some phthalate biomarkers and between pregnant and nonpregnant women for DEP.

Paternal exposure to di-n-butyl-phthalate induced developmental toxicity in zebrafish (Danio rerio)

BACKGROUND

Dibutyl phthalate (DBP) is an environmental endocrine disruptor detected in water, soil, and other environmental media frequently. Growing concerns regarding DBP exposure focus on toxicity to male reproduction. Reports about the developmental toxicity of paternal DBP exposure are rare. In this study, we investigated the developmental toxicity of paternal exposure to DBP on offspring in zebrafish.

METHODS

Adult male zebrafish with normal reproductive function were exposed to 0.2, 0.6, 1.8 mg/L of DBP or acetone solvent control for 30 days, and then mated with females. Thirty embryos per group were randomly selected to be observed, and malformations were recorded and photographed. The mating and observations were repeated three times, for a total of 90 embryos per group.

RESULTS

The results showed that the percentage of malformations, such as edema and a bent trunk, was increased in the 0.6 and 1.8 mg/L DBP exposure groups, the heart rate and spontaneous contraction decreased in the 0.6 and 1.8 mg/L DBP exposure groups and migration of primordial germ cells was disrupted in some F1 embryos in all DBP exposure group after paternal exposure. The axial skeleton was affected in some F1 adults in the 1.8 mg/L DBP exposure group.

CONCLUSIONS

Our findings demonstrate the developmental toxicity of paternal DBP exposure in zebrafish.

Insights into the microbial response of anaerobic granular sludge during long-term exposure to polyethylene terephthalate microplastics

The negative effects of ubiquitous microplastics on wastewater treatment have attracted increasing attention. However, the potential impacts of microplastics on anaerobic granular sludge (AGS) remain unknown. To fill this knowledge gap, this paper investigated the response of AGS to the exposure of model microplastics (polyethylene terephthalate (PET-MPs)) and provided insights into the mechanisms involved. The 84 days' long-term exposure experiments demonstrated that PET-MPs, at relatively low level (15 MP L^-1) did not affect AGS performance during anaerobic wastewater treatment, while 75-300 MP L^-1 of PET-MPs caused the decreases of COD removal efficiency and methane yields by 17.4-30.4% and 17.2-28.4%, accompanied with the 119.4-227.8% increase in short-chain fatty acid (SCFA) accumulation and particle breakage. Extracellular polymeric substances (EPS) analysis showed that dosage-dependent tolerance of AGS to PET-MPs was attributed to the induced EPS producing protection role, but PET-MPs at higher concentrations (75-300 MP L^-1) suppressed EPS generation. Correspondingly, microbial community analysis revealed that the populations of key acidogens (e.g., Levilinea sp.) and methanogens (e.g., Methanosaeta sp.) decreased after long-term exposure to PET-MPs. Assessment of the toxicity of PET-MPs revealed that the leached di-n-butyl phthalate (DBP) and the induced reactive oxygen species (ROS) by PET-MPs were causing toxicity towards AGS, confirmed by the increases in cell mortality and lactate dehydrogenase (LDH) release. These results provide novel insights into the ecological risk assessment of microplastics in anaerobic wastewater treatment system.

[Toxicity of dibutyl phthalate in primary cultured rat hippocampal neurons and the toxicological mechanism]

OBJECTIVE

To investigate the neurotoxicity and toxicological mechanism of dibutyl phthalate (DBP) in primary cultured rat hippocampal neurons.

METHODS

Primary rat hippocampal neurons cultured for 4 days were exposed to 1 g/L DBP for 24, 48, or 96 h. Immunofluorescence assay and transmission electron microscopy (TEM) were used to observe the morphological changes of the axons and the ultrastructure of DBP-treated neurons. The action potential (AP) of the hippocampal neurons was measured with patch-clamp electrophysiology. CCK-8 assay was used to detect the viability of the hippocampal neurons, and Western blotting was performed to determine the mRNA and protein expressions of brain-derived neurotrophic factor (BDNF), neuropeptide Y (NPY) and estrogen receptor β (ERβ). High-performance liquid chromatography-tandem mass spectrometry (HPLC-MS) was employed to detect the release of the neurotransmitter GABA.

RESULTS

After exposure to DBP for 96 h, the cellular network of the hippocampal neurons became sparse, and the neurons showed significantly decreased axonal length (P < 0.01) and presented with round cell nuclei, chromatin aggregation and cytoplasmic vacuolization. Patch-clamp electrophysiology revealed depolarization drift and increased frequency of discharge in the exposed neurons (P < 0.01). The neurons with DBP exposure for 24, 48 and 96 h all showed significantly decreased cell viability (P < 0.01). DBP exposure for 48 and 96 h significantly lowered the protein expressions of ERβ, BDNF and NPY, and a 96-h exposure significantly reduced the release of the neurotransmitter GABA in the neurons (P < 0.05).

CONCLUSIONS

DBP exposure causes morphological and functional damages of primary cultured rat hippocampal neurons. DBP-induced neurotoxicity is probably associated with GABA-mediated blockage of the ERβ-BDNF-NPY signaling communication.

Phthalate and Bisphenol Exposure during Pregnancy and Offspring Nonverbal IQ

BACKGROUND

Prenatal exposures to phthalates and bisphenols are associated with impaired brain development in animals. However, epidemiological studies investigating the association between prenatal phthalate or bisphenol exposure and cognition have produced mixed findings and mostly had modest sample sizes and measured the exposure during the third trimester.

OBJECTIVE

We examined the association between pregnancy maternal urinary biomarkers of phthalate or bisphenol exposure and nonverbal intelligence quotient (IQ) in children 6 years of age.

METHOD

The study sample consisted of 1,282 mother-child pairs participating in the Generation R Study, a population-based birth cohort in Rotterdam, Netherlands (enrollment 2002-2006). We measured maternal urinary concentrations of 18 phthalate metabolites and 8 bisphenols at < 18 , 18-25, and > 25  wks of gestation. Child nonverbal IQ was measured at 6 years of age using the Snijders-Oomen Nonverbal Intelligence Test-Revised. Linear regression models were fit for each of the three collection phases separately, the three collection phases jointly, and for the averaged prenatal exposure across pregnancy.

RESULTS

Higher urinary concentrations of phthalate metabolites during early pregnancy were associated with lower child nonverbal IQ score [e.g., B per 10-fold increase in summed low-molecular weight phthalates = - 1.7 (95% CI: - 3.1 , - 0.3 )]. This association remained unchanged when adjusted for mid and late pregnancy exposures. We also observed an inverse association between late pregnancy di-n-octyl phthalate (DNOP) exposure and nonverbal IQ. Maternal urinary concentrations of bisphenols were not associated with child nonverbal IQ. There was no effect estimate modification by sex.

CONCLUSIONS

We did not observe that maternal biomarkers of bisphenol exposure are associated with nonverbal IQ. We found that phthalate exposure in early pregnancy and DNOP exposure in late pregnancy are associated with lower nonverbal IQ scores in children. Our results might suggest that particularly early pregnancy is a sensitive window of phthalate exposure, but future studies are needed to replicate our findings. https://doi.org/10.1289/EHP6047.

Gestational and lactational exposition to di-n-butyl phthalate increases neurobehavioral perturbations in rats: A three generational comparative study

Di-n-butyl phthalate (DBP) cause significant deficits in cognition and memory, however the neuroanatomical basis for impairments remain poorly understood. This study evaluates neurobehavioral changes in rats for three successive generations between non-siblings by administering DBP at 500mg/kg bw dose through oral gavage from gestation day-6 to 21 and lactation (3-weeks). Weaning period evaluations and developmental deficits assessed showed variations specific to generation and the toxic potential of DBP was confounded by behavioral deficits that include changes in sensorimotor development reflex response, poor performance, low memory retention and greater latency period. The cytoarchitectural alterations witnessed in hippocampus include condensed nuclei, vacuole formation and remarkable degeneration, shrinkage of pyramidal neurons in CA1 and CA3 regions; disorganized hilar cells and hyperplasia in dentate gyrus. Comparatively, the enlisted changes were high in subsequent generations than preceding and correlates assessed between cognitive impairment(s) and endocrine function confirm a link indicating vulnerability of immature animals as target to disrupt neural and endocrine functions.

Dibutyl phthalate exposure during gestation and lactation in C57BL/6 mice: Maternal behavior and neurodevelopment in pups

OBJECTIVES

Neurotoxic effects of phthalate during pregnancy on immature brain of the offspring or mature brains of the mothers remain unclear. We examined the effect of dibutyl phthalate (DBP) exposure during gestation and lactation on the maternal behavior of mother mice and neurodevelopment in pups.

METHODS

Pregnant mice were treated orally with DBP (0, 50 and 100 mg/kg/day, N = 20 per group) from gestational day 13 to postnatal day (PND) 15. Maternal behavior was measured using pup retrieval and nest shape test at postpartum day 4. For the pups, the neurodevelopment was measured using negative geotaxis, cliff avoidance at PND 7, swimming test and olfactory orientation at PND 14. RNA and protein expressions in the brain cortex of 50 mg/kg/day and control group (0 mg/kg/day) were analyzed using microarray and Western blot analysis. Nissl-stained sections at the coronal level of interaural 2.56 mm, bregma -1,23 mm, were used for counting of dark cortical neurons in mother and pup mice.

RESULTS

DBP treated mother mice (50 and 100 mg/kg/day) showed poor maternal behavior, poor nesting and retrieval behavior compared to the control group (0 mg/kg/day). In brain cortex, DBP-treated mothers showed decrease in protein expression of Nr4a3, Egr1, Arc, BDNF and phosphorylation of AKT and CREB, were also decreased in cortex of DBP-treated mothers. Pups exposed to DBP showed significantly decreased scores in negative geotaxis at PND 7 and swimming scores and olfactory orientation tests at PND 14. The cortex of the DBP exposed pups showed increase in expression of dopamine receptor D2 gene. Nissl staining showed that the dark neurons were increased in cortex of DBP treated mothers and DBP exposed pups. Suggesting that phthalate may delay pup development indirectly through inadequate mothering as well as direct phthalate exposure on the brain.

CONCLUSION

DBP exposure during gestation and lactation cause impairment in maternal behaviors and downregulation of neuronal plasticity and survival signals. Pups of mothers with exposed to DBP, showed delayed neurodevelopment and dark neurons increase in brain cortex, suggesting that phthalate may delay pup development indirectly through inadequate mothering as well as direct phthalate exposure on the brain.

DEHP triggers cerebral mitochondrial dysfunction and oxidative stress in quail (Coturnix japonica) via modulating mitochondrial dynamics and biogenesis and activating Nrf2-mediated defense response

Di-(2-ethylhexyl) phthalate (DEHP) in the environment and food chain may impact cerebrum development and neurobehavioral in humans and wildlife. However, it is unclear that DEHP exposure caused cerebral toxicity. This experiment used gavage to expose female quail to 0, 250, 500, and 1000 mg/kg BW/day for 45 days to assess the potential neurotoxicity of DEHP to the cerebrum. It can be observed that there will be obvious neurological abnormalities in the experiment. Cerebrum histological lesions can be observed with HE-staining. Detecting oxidative stress indices, Nrf2 pathway, and mitochondrial dynamics factor, by analyzing the results, these results were observed that DEHP exposure can cause damage to the cerebrum by causing oxidative stress and affecting the balance of mitochondrial dynamics. Nrf2-mediated defense is not activated by exposure to 250 mg/kg DEHP. Nrf2-mediated defense is activated but is not resistant to exposure to medium and high doses of DEHP (500 mg/kg; 1000 mg/kg). DEHP triggers cerebral mitochondrial dysfunction via modulating mitochondrial dynamics.

Identifying periods of susceptibility to the impact of phthalates on children's cognitive abilities

BACKGROUND

Early-life phthalate exposures may adversely affect children's neurodevelopment by disrupting thyroid function, reducing gonadal hormone levels, or altering fatty acid concentrations in the brain. This study aimed to identify periods of heightened susceptibility during gestation, infancy, and childhood to the impact of phthalates on children's cognitive abilities.

METHODS

We used data from 253 mother-child pairs in the Health Outcomes and Measures of the Environment (HOME) Study (Cincinnati, Ohio), a longitudinal pregnancy and birth cohort. We quantified urinary concentrations of 11 phthalate metabolites in samples collected twice during gestation and 6 times during study visits when children were aged 1-8 years using a modified method of on-line solid phase extraction coupled with isotope dilution-high performance liquid chromatography-tandem mass spectrometry. We assessed children's intelligence (IQ) at ages 5 and 8 years using the Wechsler Preschool and Primary Scale of Intelligence-III and Wechsler Intelligence Scale for Children-IV, respectively. We estimated covariate-adjusted associations between a 1-standard deviation increase in log10-transformed urinary phthalate metabolite concentrations at each visit and children's IQ, adjusting for demographic, perinatal, and child factors; we tested for differences in these associations across visits using multiple informant models.

RESULTS

Associations between some phthalate metabolites and IQ varied by visit (phthalate x visit interaction p-values<0.20). The sum of di(2-ethylhexyl) phthalate metabolites (ΣDEHP), mono(3-carboxypropyl) phthalate, and monoethyl phthalate at age 3 years, and monobenzyl phthalate at 16 weeks gestation and child ages 3, 5, and 8 years were inversely associated with children's full-scale IQ. For example, each 1-standard deviation increase in ΣDEHP at age 3 was associated with a 1.9-point decrease in full-scale IQ (95% confidence interval: -3.7, -0.2). Mono-n-butyl phthalate and mono-isobutyl phthalate at age 4 years were positively associated with children's full-scale IQ.

CONCLUSION

Urinary concentrations of several phthalate metabolites at age 3 years, compared to other time periods, were more strongly associated with decreased cognitive abilities in these children.

A Review of Biomonitoring of Phthalate Exposures

Phthalates (diesters of phthalic acid) are widely used as plasticizers and additives in many consumer products. Laboratory animal studies have reported the endocrine-disrupting and reproductive effects of phthalates, and human exposure to this class of chemicals is a concern. Several phthalates have been recognized as substances of high concern. Human exposure to phthalates occurs mainly via dietary sources, dermal absorption, and air inhalation. Phthalates are excreted as conjugated monoesters in urine, and some phthalates, such as di-2-ethylhexyl phthalate (DEHP), undergo secondary metabolism, including oxidative transformation, prior to urinary excretion. The occurrence of phthalates and their metabolites in urine, serum, breast milk, and semen has been widely reported. Urine has been the preferred matrix in human biomonitoring studies, and concentrations on the order of several tens to hundreds of nanograms per milliliter have been reported for several phthalate metabolites. Metabolites of diethyl phthalate (DEP), dibutyl- (DBP) and diisobutyl- (DiBP) phthalates, and DEHP were the most abundant compounds measured in urine. Temporal trends in phthalate exposures varied among countries. In the United States (US), DEHP exposure has declined since 2005, whereas DiNP exposure has increased. In China, DEHP exposure has increased since 2000. For many phthalates, exposures in children are higher than those in adults. Human epidemiological studies have shown a significant association between phthalate exposures and adverse reproductive outcomes in women and men, type II diabetes and insulin resistance, overweight/obesity, allergy, and asthma. This review compiles biomonitoring studies of phthalates and exposure doses to assess health risks from phthalate exposures in populations across the globe.

Combined use of vitamin E and nimodipine ameliorates dibutyl phthalate-induced memory deficit and apoptosis in mice by inhibiting the ERK 1/2 pathway

Learning disabilities (LDs) in children are a serious global problem. Dibutyl phthalate (DBP), a plasticizer widely used in daily life, has been linked to triggering childhood LDs, however the mechanism underlying this remains unclear. Studies have shown that the ERK 1/2 pathway is closely related to apoptosis of hippocampal neurons. On the basis of these links between LDs, DBP and the ERK 1/2 pathway, we explore whether DBP induces hippocampal neuron apoptosis and increases behavioral disorders in mice via the ERK 1/2 pathway. We looked at oxidative stress, examined the calcium signal, detected the ERK 1/2 pathway and evaluated apoptosis as well as using histological observations, and found that DBP significantly increased oxidative damage and apoptosis in hippocampal neurons via the ERK 1/2 pathway in mice. We also found that pretreatment with the dihydropyridine's (DHP's) Ca²⁺ antagonist, nimodipine (NMDP), combined with the antioxidant Vitamin E (VE), attenuated ERK 1/2 phosphorylation and DBP-mediated disorders, suggesting that a combined use of VE and NMDP can ameliorate DBP-induced memory deficit and apoptosis via inhibiting the ERK 1/2 pathway. These results indicate that DBP predisposes oxidative damage and apoptosis in hippocampal neurons by activation of the ERK 1/2 pathway, and may be proposed as a possible mechanism underlying LDs in children. Moreover, VE and NMDP may play a certain protective role in the targeted treatment of childhood LDs.

Neurochemical alterations following the exposure to di-n-butyl phthalate in rats

Due to its ability to cross blood brain barrier and placenta, dibutyl phthalate (di-n-butyl phthalate, DBP) is expected to cause severe side effects to the central nervous system of animals and humans. A little data is available about the potential DBP neurotoxicity; therefore, this work was designed to investigate the brain tissue injury induced by DBP exposure. Forty Wister albino rats were allocated randomly into 4 groups (10 rats each). Group 1 served as control and the rats administered with physiological saline (0.9% NaCl) orally for 12 weeks. Groups 2, 3 and 4 were orally treated with DPB (100, 250 and 500 mg/kg) respectively for 12 weeks. DBP-intoxicated rats showed a disturbance in the oxidative status in cerebral cortex, striatum and brainstem, as represented by the elevated oxidants [malondialdehyde (MDA), nitric oxide (NO), 8-hydroxy-2-deoxyguanosine (8-OHdG)] and the decreased antioxidant molecules [reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR)]. DBP also enhanced a pro-inflammatory state through increasing the release of tumor necrosis factor- α (TNF-α) and interleukin-1β (IL-1β). The increase of these cytokines was associated with the increase of pro-apoptotic proteins [Bcl-2 associated X protein (Bax) and caspase-3] and the decrease of the anti-apoptotic protein, B cell lymphoma 2 (Bcl-2). In addition, the levels of norepinephrine (NE), dopamine (DA) and acetylcholine esterase (AChE) activity were decreased. This was accompanied by the alterations in the major excitatory and inhibitory amino acids neurotransmitters levels. The present findings indicated that DBP could exert its neuronal damage through oxidative stress, DNA oxidation, neuroinflammation, activation of apoptotic proteins and altering the monoaminergic, cholinergic and amino acids transmission.

Prenatal exposure to phthalates and autism spectrum disorder in the MARBLES study

BACKGROUND

Evidence from experimental and observational studies suggests that prenatal phthalate exposures may be associated with autism spectrum disorder (ASD). We examined whether prenatal phthalate exposures were associated with an increased risk of ASD.

METHODS

We quantified 14 metabolites of eight phthalates in 636 multiple maternal urine samples collected during 2nd and 3rd trimesters of pregnancy from 201 mother-child pairs in MARBLES (Markers of Autism Risk in Babies - Learning Early Signs), a high-risk ASD longitudinal cohort. At 3 years old, children were clinically assessed for ASD and classified into three diagnostic categories: ASD (n = 46), non-typical development (Non-TD, n = 55), and typical development (TD, n = 100). We used multinomial logistic regression to evaluate the association of phthalate metabolite concentrations with ASD and Non-TD.

RESULTS

Most associations of phthalate biomarkers with both ASD and Non-TD were null, with the exception that monoethyl phthalate (MEP) was significantly associated with an increased risk of Non-TD (per 2.72-fold relative increase in concentration: Relative risk ratio (RRR) = 1.38; 95% confidence interval (CI): 1.01, 1.90). When stratified by prenatal vitamin use during the first month of pregnancy, among mothers who took vitamins, ASD risk was inversely associated with mono-isobutyl phthalate (MiBP, RRR = 0.44; 95% CI: 0.21, 0.88), mono(3-carboxypropyl) phthalate (MCPP, RRR = 0.41; 95% CI: 0.20, 0.83) and mono-carboxyisooctyl phthalate (MCOP, RRR = 0.49; 95% CI: 0.27, 0.88), but among mothers who did not take prenatal vitamins, Non-TD risk was positively associated with MCPP (RRR = 5.09; 95% CI: 2.05, 12.6), MCOP (RRR = 1.86; 95% CI: 1.01, 3.39), and mono-carboxyisononyl phthalate (MCNP, RRR = 3.67; 95% CI: 1.80, 7.48). When stratified by sex, among boys, MEP, monobenzyl phthalate, MCPP, MCNP, and sum of di(2-ethylhexyl) phthalate metabolites (ΣDEHP) were positively associated with Non-TD risk, but associations with ASD were null. Among girls, associations with both ASD and Non-TD were null.

CONCLUSIONS

Our study showed that phthalate exposures in mid- to late pregnancy were not associated with ASD in children from this high-risk ASD cohort. Further studies should be conducted in the general population without high-risk genes to confirm our findings.

Association of Prenatal Phthalate Exposure With Language Development in Early Childhood

IMPORTANCE

Prenatal exposure to phthalates has been associated with neurodevelopmental outcomes, but little is known about the association with language development.

OBJECTIVE

To examine the association of prenatal phthalate exposure with language development in children in 2 population-based pregnancy cohort studies.

DESIGN, SETTING, AND PARTICIPANTS

Data for this study were obtained from the Swedish Environmental Longitudinal Mother and Child, Asthma and Allergy (SELMA) study conducted in prenatal clinics throughout Värmland county in Sweden and The Infant Development and the Environment Study (TIDES) conducted in 4 academic centers in the United States. Participants recruited into both studies were women in their first trimester of pregnancy who had literacy in Swedish (SELMA) or English or Spanish (TIDES). This study included mothers and their children from both the SELMA study (n = 963) and TIDES (n = 370) who had complete data on prenatal urinary phthalate metabolite levels, language delay, and modeled covariables. For SELMA, the data were collected from November 1, 2007, to June 30, 2013, and data analysis was conducted from November 1, 2016, to June 30, 2018. For TIDES, data collection began January 1, 2010, and ended March 29, 2016, and data analysis was performed from September 15, 2016, to June 30, 2018.

MAIN OUTCOMES AND MEASURES

Mothers completed a language development questionnaire that asked the number of words their children could understand or use at a median of 30 months of age (SELMA) and 37 months of age (TIDES). The responses were categorized as fewer than 25, 25 to 50, and more than 50 words, with 50 words or fewer classified as language delay.

RESULTS

In the SELMA study, 963 mothers, 455 (47.2%) girls, and 508 (52.8%) boys were included. In TIDES, 370 mothers, 185 (50.0%) girls, and 185 (50.0%) boys were included in this analysis. The prevalence of language delay was 10.0% in both SELMA (96 reported) and TIDES (37 reported), with higher rates of delay in boys than girls (SELMA: 69 [13.5%] vs 27 [6.0%]; TIDES: 23 [12.4%] vs 14 [7.6%]). In crude analyses, the metabolite levels of dibutyl phthalate and butyl benzyl phthalate were statistically significantly associated with language delay in both cohorts. In adjusted analyses, a doubling of prenatal exposure of dibutyl phthalate and butyl benzyl phthalate metabolites increased the odds ratio (OR) for language delay by approximately 25% to 40%, with statistically significant results in the SELMA study (dibutyl phthalate OR, 1.29 [95% CI, 1.03-1.63; P = .03]; butyl benzyl phthalate OR, 1.26 [95% CI, 1.07-1.49; P = .003]). A doubling of prenatal monoethyl phthalate exposure was associated with an approximately 15% increase in the OR for language delay in the SELMA study (OR, 1.14; 95% CI, 1.00-1.31; P = .05), but no such association was found in TIDES (OR, 0.98; 95% CI, 0.79-1.23).

CONCLUSIONS AND RELEVANCE

In findings from this study, prenatal exposure to dibutyl phthalate and butyl benzyl phthalate was statistically significantly associated with language delay in children in both the SELMA study and TIDES. These findings, along with the prevalence of prenatal exposure to phthalates, the importance of language development, and the inconsistent results from a 2017 Danish study, suggest that the association of phthalates with language delay may warrant further examination.

Involvement of oxidative stress in di-2-ethylhexyl phthalate (DEHP)-induced apoptosis of mouse NE-4C neural stem cells

Di-2-ethylhexyl phthalate (DEHP) has been widely used as a plasticizer in industry and can cause neurotoxicity; however, the underlying mechanism remains unclear. In the study, we found that DEHP significantly inhibited viability of mouse NE-4C neural stem cells and caused lactate dehydrogenase (LDH) release from the cells. DEHP dramatically increased the levels of apoptosis-related proteins such as cleaved Caspase-8, cleaved Caspase-3 and Bax, as well as decreased Bcl-2 protein level. DEHP could also significantly increase the total numbers of AnnexinV-positive/PI-negative and AnnexinV-positive/PI-positive staining cells. Hoechst 33342 staining showed that marked DNA condensation and apoptotic bodies could be found in the ZnO NPs-treated cells. These results indicated that DEHP could induce apoptosis of NE-4C cells. Meanwhile, DEHP could significantly increase malondialdehyde (MDA) level, and decrease the content of glutathione (GSH) and activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX), respectively, implying that DEHP could induce oxidative stress of NE-4C cells. Furthermore, N-Acetyl-l-cysteine (NAC), an inhibitor of oxidative stress, could rescue the inhibition of cell viability and induction of apoptosis by DEHP. Taken together, our results showed that oxidative stress was involved in DEHP-induced apoptosis of mouse NE-4C cells.

New insights into the mechanism of phthalate-induced developmental effects

To investigate the biological pathways involved in phthalate-induced developmental effects, zebrafish embryos were exposed to different concentrations of di-(2-ethylhexyl) (DEHP) and di-butyl phthalate (DBP) for 96 h. Embryonic exposure to DEHP and DBP induced body length decrease, yolk sac abnormities, and immune responses (up-regulation of immune proteins and genes). The lipidomic results showed that at a concentration of 50 μg/L, DEHP and DBP significantly reduced the levels of fatty acids, triglycerides, diacylglycerol, and cholesterol. These effects are partly explained by biological pathway enrichment based on data from the transcriptional and proteomic profiles. Co-exposure to DBP and ER antagonist did not significantly relieve the toxic symptoms compared with exposure to DBP alone. This indicates that phthalate-induced developmental abnormities in zebrafish might not be mediated by the ER pathway. In conclusion, we identified the possible biological pathways that mediate phthalate-induced developmental effects and found that these effects may not be driven by estrogenic activation.

Effects of Perinatal Exposure to Phthalates and a High-Fat Diet on Maternal Behavior and Pup Development and Social Play

Humans are ubiquitously exposed to many phthalates, a class of endocrine-disrupting chemicals commonly used in many consumer goods, and diet, especially fatty food, is presumed to be a major source of exposure. Here, we use a rat model of human prenatal exposure to investigate the potential interactive effects of an environmentally relevant mixture of phthalates and a maternal high-fat diet (HFD). From gestation through postnatal day (P)10, dams consumed the mixture of phthalates (0, 200, or 1000 μg/kg/d) and were fed a control diet or HFD. In males, perinatal exposure to the mixture of phthalates decreased prepubertal body weight and, in a dose-specific manner, periadolescent social play behavior. A dose-specific effect from phthalates with HFD was also seen in increased time alone in females during social play. HFD resulted in dams consuming more calories, having greater gestational weight gain, and licking and nursing their pups more, such that an early postnatal HFD generally increased pup body weight. There also was a tendency for increased oxidative stress markers at P10 within the medial prefrontal cortex of males exposed to the relatively high dose of phthalates and HFD. Effects on gene expression were inconsistent at P10 and P90 in both the medial prefrontal cortex and hypothalamus. Overall, this study demonstrates that phthalates and a maternal HFD only rarely interacted, except in oxidative stress markers in males. Additionally, perinatal exposure to an environmentally relevant mixture of phthalates can have a modest, but lasting, impact on social behaviors in both males and females.

Paternal and maternal preconception urinary phthalate metabolite concentrations and child behavior

BACKGROUND

Prenatal phthalate exposure has been associated with behavioral problems and lower performance on measures of cognitive ability in children. However, the potential effect of phthalate exposure during the sensitive preconception period is unknown.

OBJECTIVES

To estimate the association of maternal and paternal preconception urinary phthalate metabolite concentrations with child behavior and evaluate potential modification by child sex.

METHODS

We used data from 166 children (111 singletons, 26 pairs of twins, and 1 set of triplets) born to 134 mothers and 100 fathers participating in a prospective preconception cohort study of subfertile couples from the Massachusetts General Hospital Fertility Center. We estimated mean maternal and paternal preconception exposures by averaging individual phthalate metabolite concentrations in multiple urine samples collected before pregnancy. We assessed children's behavior at 2-9 years of age by parent report using the Behavior Assessment System for Children-2 (BASC-2). We estimated the covariate-adjusted association between individual phthalate metabolite concentrations and the sum of di(2-ethylhexyl) phthalate metabolites (∑ DEHP) and behavior scores, and evaluated differences in associations by child sex using linear regression with Generalized Estimating Equations. Models were further adjusted for prenatal phthalate concentrations in sensitivity analyses.

RESULTS

Each loge-unit increase in maternal and paternal preconception concentrations of ∑DEHP was associated with a 2.0 (95% CI: - 3.2, - 0.7) and 1.8 (95% CI: - 3.1, - 0.4) point decrease in BASC-2 internalizing behavior scores among all children, respectively. We observed sex-specific associations for some phthalate biomarkers: among boys, maternal monoisobutyl phthalate (MiBP) was positively associated with externalizing behaviors, and paternal MiBP and mono-n-butyl phthalate were positively associated with internalizing behaviors.

CONCLUSIONS

In this cohort, paternal and maternal preconception concentrations of some phthalate biomarkers were associated with specific aspects of child behavior, even after adjustment for prenatal concentrations. While additional research is warranted to confirm these results, our findings suggest that the preconception period of exposure may be a critical window for offspring neurodevelopment.

A novel nuclear xenobiotic receptors (AhR/PXR/CAR)-mediated mechanism of DEHP-induced cerebellar toxicity in quails (Coturnix japonica) via disrupting CYP enzyme system homeostasis

Di-(2-ethylhexyl)-phthalate (DEHP) is causing serious health hazard in wildlife animal and human through environment and food chain, including the effect of brain development and impacted neurobehavioral outcomes. However, DEHP exposure caused cerebellar toxicity in bird remains unclear. To evaluate DEHP-exerted potential neurotoxicity in cerebellum, male quails were exposed with 0, 250, 500 and 750 mg/kg BW/day DEHP by gavage treatment for 45 days. Neurobehavioral abnormality and cerebellar histopathological alternation were observed in DEHP-induced quails. DEHP exposure increased the contents of total Cytochrome P450s (CYPs) and Cytochrome b5 (Cyt b5) and the activities of NADPH-cytochrome c reductase (NCR) and aniline-4-hydeoxylase (AH) in quail cerebellum. The expression of nuclear xenobiotic receptors (NXRs) and the transcriptions of CYP enzyme isoforms were also influenced in cerebellum by DEHP exposure. These results suggested that DEHP exposure caused the toxic effects of quail cerebellum. DEHP exposure disrupted the cerebellar CYP enzyme system homeostasis via affecting the transcription of CYP enzyme isoforms. The cerebellar P450arom and CYP3A4 might be biomarkers in evaluating the neurotoxicity of DEHP in bird. Finally, this study provided new evidence that DEHP-induced toxic effect of quail cerebellum was associated with activating the NXRs responses and disrupting the CYP enzyme system homeostasis.

Gestational di-n-butyl phthalate exposure induced developmental and teratogenic anomalies in rats: a multigenerational assessment

With the limited but ongoing usage of di-n-butyl phthalate (DBP) as plasticizer, the health effects of both phthalate and its alternatives are far from being understood. Multigenerational effects of phthalates were evaluated in rats upon exposure to DBP, aiming to provide some evidences about its potential in causing developmental teratogenicity. Gestational rats were exposed to DBP (500 mg/kg bw/day) and control groups with olive oil. On the 18th day of gestation, fetuses (F₁) isolated from a few dams were subjected to prenatal screening, and the other rats were allowed to litter, and later postnatal screening was made. DBP-toxicated (F₁) rats were crossed and reared up to three generations (F₂ and F₃) by adopting the same experimental design. A considerable decrease in the weight of placenta, low number of corpora lutea and increased resorptions, and pre- and postimplantation loss were observed in F₁, F₂, and F₃ generations. Further, there was a decrease in the number of live births and fetal body weight with high mortality, the developmental indices showed reduction in litter size and sex ratio, and a considerable incidence of skeletal and malformation complex involving face and eye was observed in later generations compared to the first. The pre-weaning indices in neonates showed a considerable delay in physical growth milestones and poor scores in sensory motor development. Alterations noticed in the levels of thyroid profile and testosterone found to have a role in sensory motor, craniofacial development, and eye formation. In brief, results confirm multigenerational and fetotoxic effects of DBP; thereby, findings imply that developing tissues are the targets and endocrine disruption appears to be the underlying mechanism of phthalate action.

Prenatal phthalate, triclosan, and bisphenol A exposures and child visual-spatial abilities

INTRODUCTION

During fetal development, sex steroids influence sexually dimorphic behaviors, such as visual-spatial abilities. Thus, endocrine disrupting chemicals that impact sex steroids during gestation may affect these behaviors.

OBJECTIVE

We investigated the relationship between prenatal urinary phthalate metabolite, triclosan, and BPA concentrations and visual-spatial abilities in a prospective cohort of 198 mother-child dyads.

METHODS

Data are from a prospective cohort in Cincinnati, OH (HOME Study). We measured nine phthalate metabolites, triclosan, and BPA in maternal urine samples collected at 16 and 26 weeks of gestation. We assessed children's visual-spatial abilities at 8 years of age using the Virtual Morris Water Maze (VMWM), a computerized version of the rodent Morris Water Maze. We quantified the covariate-adjusted change in the time or distance to complete the VMWM and time spent in the correct quadrant during a probe trial with an interquartile range increase in chemical concentrations using linear mixed models and linear regression, respectively.

RESULTS

Boys completed the VMWM faster (4.1s; 95% CI:-7.1, -1.2) and in less distance (1.4 units; 95% CI:-2.8, 0) than girls. Overall, children with higher mono-n-butyl (MnBP), mono-benzyl (MBzP), and mono-carboxypropyl phthalate concentrations completed the VMWM in less time and distance than children with lower concentrations. For example, children with higher MnBP concentrations completed the VMWM in 0.9 less distance units (95% CI:-1.8, -0.0). Child sex modified the association between MnBP and VMWM performance. In girls, higher MnBP concentrations were associated with longer time (1.7s; 95% CI: -0.7, 4.1) and shorter distance (-1.7 units; 95% CI: -2.8, -0.5), whereas in boys, it was associated with shorter time (-3.0s; 95% CI:-5.6, -0.4), but not distance (-0.1 units; 95% CI:1.4, 1.0). Other phthalate metabolites, triclosan, and BPA were not associated with VMWM performance, and sex did not consistently modify these associations.

CONCLUSIONS

In this cohort, greater prenatal urinary concentrations of some phthalate metabolites were associated with improved VMWM performance, particularly among boys. Future studies should confirm these findings and determine if phthalates affect other hormonally sensitive aspects of child neurobehavior.

Dibutyl Phthalate (DBP)-Induced Apoptosis and Neurotoxicity are Mediated via the Aryl Hydrocarbon Receptor (AhR) but not by Estrogen Receptor Alpha (ERα), Estrogen Receptor Beta (ERβ), or Peroxisome Proliferator-Activated Receptor Gamma (PPARγ) in Mouse Cortical Neurons

Dibutyl phthalate (di-n-butyl phthalate, DBP) is one of the most commonly used phthalate esters. DBP is widely used as a plasticizer in a variety of household industries and consumer products. Because phthalates are not chemically bound to products, they can easily leak out to enter the environment. DBP can pass through the placental and blood–brain barriers due to its chemical structure, but little is known about its mechanism of action in neuronal cells. This study demonstrated the toxic and apoptotic effects of DBP in mouse neocortical neurons in primary cultures. DBP stimulated caspase-3 and LDH activities as well as ROS formation in a concentration (10 nM–100 µM) and time-dependent (3–48 h) manner. DBP induced ROS formation at nanomolar concentrations, while it activated caspase-3 and LDH activities at micromolar concentrations. The biochemical effects of DBP were accompanied by decreased cell viability and induction of apoptotic bodies. Exposure to DBP reduced Erα and Pparγ mRNA expression levels, which were inversely correlated with protein expression of the receptors. Treatment with DBP enhanced Ahr mRNA expression, which was reflected by the increased AhR protein level observed at 3 h after exposure. ERα, ERβ, and PPARγ antagonists stimulated DBP-induced caspase-3 and LDH activities. AhR silencing demonstrated that DBP-induced apoptosis and neurotoxicity are mediated by AhR, which is consistent with the results from DBP-induced enhancement of AhR mRNA and protein expression. Our study showed that AhR is involved in DBP-induced apoptosis and neurotoxicity, while the ERs and PPARγ signaling pathways are impaired by the phthalate.

Gestational exposure to phthalates and gender-related play behaviors in 8-year-old children: an observational study

BACKGROUND

Phthalates, used in a variety of consumer products, are a group of chemicals that are ubiquitous in the environment, and their metabolites are detectable in most humans. Some phthalates have anti-androgenic properties; a prior study reported an association between gestational exposure to phthalates and reduced masculine behaviors in preschool boys.

METHODS

Concentrations of 9 phthalate metabolites were measured in urine collected at 16 and 26 weeks' gestation from pregnant women enrolled in the HOME Study, a prospective pregnancy and birth cohort. Measures of gender-related play were collected at 8 years of age, including the Gender Identity Questionnaire (GIQ) completed by mothers, and the Playmate and Play Style Preferences Structured Interview (PPPSI) completed by children. We examined these measures as continuous variables using both bivariate and multivariable approaches with adjustment for covariates. Additional analyses included logistic regression of GIQ and PPPSI scores dichotomized by sex at the lower 25th percentile, indicating the least typical behavior.

RESULTS

Mothers' phthalate metabolite concentrations during pregnancy were similar to the reported national average among US women. All children scored within a typical range on both measures of gender-related play behavior. No statistically significant associations were found between averaged maternal phthalate metabolite concentrations and continuous PPPSI scores or any GIQ scores. For the dichotomized PPPSI; higher maternal monoethyl phthalate (MEP) concentrations were associated with more typical play behaviors for females (OR = 0.70, CI = 0.51-0.97). In contrast, higher maternal mono-isobutyl phthalate (MiBP) concentrations were associated with higher odds of membership in the least typical play behaviors group for males (OR = 1.69, CI = 1.00-2.86).

CONCLUSIONS

In this sample of typically developing children, higher maternal urinary MEP concentrations during pregnancy were associated with more typical gender-related play behaviors in both males and females, and increased urinary MiBP concentrations were associated with less masculine gender-related play behaviors in males.

Oxidative stress mediates dibutyl phthalateinduced anxiety-like behavior in Kunming mice

Among all phthalate esters, dibutyl phthalate (DBP) is only second to di-(2-ethylhexyl) phthalate (DEHP) in terms of adverse health outcomes, and its potential cerebral neurotoxicity has raised concern in recent years. DBP exposure has been reported to be responsible for neurobehavioral effects and related neurological diseases. In this study, we found that neurobehavioral changes induced by DBP may be mediated by oxidative damage in the mouse brain, and that the co-administration of Mangiferin (MAG, 50mg/kg/day) may protect the brain against oxidative damage caused by DBP exposure. The results of ethological analysis (elevated plus maze test and open-field test), histopathological examination of the brain, and assessments of oxidative stress (OS) in the mouse brain showed that there is a link between oxidative stress and anxiety-like behavior produced by DBP at higher doses (25 or 125mg/kg/day). Biomarkers of oxidative stress encompass reactive oxygen species (ROS), glutathione (GSH), malondialdehyde (MDA) and DPC coefficients (DPC). MAG (50mg/kg/day),administered as an antioxidant,can attenuatetheanxiety-like behavior of the tested mice.

An ultra-sensitive monoclonal antibody-based enzyme-linked immunosobent assay for dibutyl phthalate in human urinary

Dibutyl phthalate (DBP) has been extensively used as a plasticizer in many daily products, which is highly toxic to human, notably affecting the reproductive and developmental function. As the previous method is expensive, time-consuming, low sensitivity and just focused on the environment. Present study was aimed to establish an ultra-sensitive and simple method based on good quality monoclonal antibody, applying to evaluate excretion level of DBP in urine samples of Chinese population directly. A monoclonal antibody was generated and characterized after fusion of myeloma cells with spleen cells isolated from BALB/c mouse. The mouse was previously immunized using a specially designed amino derivative of DBP conjugated with bovine serum albumin (BSA) as immunogen. Cross-reactivity values of the monoclonal antibody against DBP, di-isobutyl phthalate (DIBP) were observed 100% and 1.25%, while for dimethyl phthalate (DMP), butyl benzyl phthalate (BBP) and didecyl phthalate (DDP) the values were <0.06%. The standard curve was constructed at 0-50 ng mL(-1) and good linearity (R(2)=0.994) was achieved. The observed IC50 (7.34 ng mL(-1)) and LOD (0.06 ng mL(-1)) values was improved 1000-fold to polyclonal antibody and 5-fold to other monoclonal antibodies. A total 1246 urine samples were analyzed and the detection frequency of DBP was observed 72.87% by ic-ELISA. The 95th percentile and mean concentration of DBP were 12.07 and 3.00 ng mL(-1). Acceptable recovery rates of DBP were 97.8-114.3% and coefficients variation 5.93-11.09%. The concentrations of DBP in females were found significantly higher (p<0.05) than males. Similarly, the DBP in middle aged and low educated individuals was found higher (p<0.001) than the others. Considering the adverse health effects, DBP internal exposure in the Chinese population should be reduced. The ic-ELISA method has been proved as a cost effective, specific, and highly sensitive screening tool to detect DBP in urinary samples.

Effects of uterine and lactational exposure to di-(2-ethylhexyl) phthalate on spatial memory and NMDA receptor of hippocampus in mice

Di-(2-ethylhexyl) phthalate (DEHP) is an environmental endocrine disrupter. Currently, little is known about neurodevelopmental toxicity of DEHP in wildlife and humans. The present study investigated the effects of DEHP, focusing on the changes in the behavior of offspring mice at the ages of 6 and 12w, respectively, following utero and lactational exposure to DEHP (10, 50, and 200mg/kg/d) from gestation day 7 through postnatal day 21. The results of open field tasks showed that DEHP increased the grooming of males at age 6w and females at age 12w but decreased the frequency of rearing of 6-w-old females and the number of grid crossings of 12-w-old females. In the Morris water maze task, 50 and 200mg/kg/d DEHP significantly prolonged the time of searching the hidden platform in water maze and reduced the time staying in the target quadrant during a probe trial of 6-w-old male mice, but not of 6-w-old females nor 12-w-old mice of both sexes, suggesting an impaired spatial learning and memory among younger males after perinatal exposure to DEHP. Western blot analyses further showed that DEHP at 50 and 200mg/kg/d decreased the levels of the N-methyl-d-aspartic acid (NMDA) receptor subunits NR1 and NR2B in the hippocampus of 6-w-old males. These results suggest that uterine and lactational exposure to low doses of DEHP sex-specifically impacted behaviors, including locomotion activity and spatial memory, via the concomitant inhibition of the NMDA receptor of the hippocampus in offspring mice.

Prenatal exposure to phthalate esters and behavioral syndromes in children at 8 years of age: Taiwan Maternal and Infant Cohort Study

BACKGROUND

Few studies have shown an association between prenatal phthalate exposure and adverse effects on neurodevelopment and behavior in young children.

OBJECTIVES

We aimed to assess the relationship between prenatal exposure to phthalate esters and behavior syndromes in children at 8 years of age.

METHODS

A total of 122 mother-child pairs from the general population in central Taiwan were studied from 2000 to 2009. Mono-methyl phthalate (MMP), mono-ethyl phthalate (MEP), mono-butyl phthalate (MBP), mono-benzyl phthalate (MBzP), and three di-(2-ethylhexyl) phthalate (DEHP) metabolites-mono-2-ethylhexyl, mono-2-ethyl-5-hydroxyhexyl, and mono-2-ethyl-5-oxohexyl phthalates (MEHP, MEHHP, and MEOHP)--were measured in maternal urine collected during the third trimester of pregnancy using liquid chromatography-electrospray ionization-tandem mass spectrometry. Behavioral syndromes of children at 8 years of age were evaluated using the Child Behavior Checklist (CBCL). Associations between log10-transformed creatinine-corrected phthalate concentrations and standardized scores of the CBCL were estimated using linear regression models or multinomial logistic regressions with adjustments for potential confounders.

RESULTS

Externalizing problem scores were significantly higher in association with a 1-unit increase in log10-transformed creatinine-corrected concentrations of maternal MBP (β = 4.29; 95% CI: 0.59, 7.99), MEOHP (β = 3.74; 95% CI: 1.33, 6.15), and MEHP (β = 4.28 ; 95% CI: 0.03, 8.26) after adjusting for the child's sex, intelligence, and family income. Meanwhile, MBP and MEOHP were significantly associated with Delinquent Behavior and Aggressive Behavior scores. The same pattern was found for borderline and/or clinical ranges.

CONCLUSIONS

Our findings suggest positive associations between maternal DEHP and dibutyl phthalate (DBP) exposure and externalizing domain behavior problems in 8-year-old children.

Persistent Associations between Maternal Prenatal Exposure to Phthalates on Child IQ at Age 7 Years

Background

Prior research reports inverse associations between maternal prenatal urinary phthalate metabolite concentrations and mental and motor development in preschoolers. No study evaluated whether these associations persist into school age.

Methods

In a follow up of 328 inner-city mothers and their children, we measured prenatal urinary metabolites of di-n-butyl phthalate (DnBP), butylbenzyl phthalate (BBzP), di-isobutyl phthalate (DiBP), di-2-ethylhexyl phthalate and diethyl phthalate in late pregnancy. The Wechsler Intelligence Scale for Children, 4th edition was administered at child age 7 years and evaluates four areas of cognitive function associated with overall intelligence quotient (IQ).

Results

Child full-scale IQ was inversely associated with prenatal urinary metabolite concentrations of DnBP and DiBP: b = −2.69 (95% confidence interval [CI] = −4.33, −1.05) and b = −2.69 (95% CI = −4.22, −1.16) per log unit increase. Among children of mothers with the highest versus lowest quartile DnBP and DiBP metabolite concentrations, IQ was 6.7 (95% CI = 1.9, 11.4) and 7.6 (95% CI = 3.2, 12.1) points lower, respectively. Associations were unchanged after control for cognition at age 3 years. Significant inverse associations were also seen between maternal prenatal metabolite concentrations of DnBP and DiBP and child processing speed, perceptual reasoning and working memory; DiBP and child verbal comprehension; and BBzP and child perceptual reasoning.

Conclusion

Maternal prenatal urinary metabolite concentrations measured in late pregnancy of DnBP and DiBP are associated with deficits in children’s intellectual development at age 7 years. Because phthalate exposures are ubiquitous and concentrations seen here within the range previously observed among general populations, results are of public health significance.

Dibutyl phthalate-induced neurotoxicity in the brain of immature and mature rat offspring

PURPOSE

We aim to investigate the neurotoxicity induced by perinatal exposure of dibutyl phthalate (DBP) on the immature and mature offspring animals using a rodent model.

METHODS

Pregnant rats were given intragastric administration of 500mg/kg body weight DBP daily from gestational day 6 to postnatal day 21 while control animals received the same volume of edible corn oil. Serum estradiol and testosterone levels of the offspring were evaluated. Protein levels of AROM, ER-β, BDNF and p-CREB in the hippocampus were also measured.

RESULTS

Perinatal exposure of DBP significantly up-regulated the serum estradiol levels in both immature and mature offspring rats. DBP exposure also significantly down-regulated the testosterone levels in immature male and female rats and mature male rats but had no influence on the testosterone levels in mature female rats. DBP exposure up-regulated AROM, but down-regulated ER-β, BDNF and p-CREB expression in the hippocampus of immature rat offspring, while it had no influence on the levels of these proteins in the mature animals.

CONCLUSIONS

Perinatal exposure of DBP could induce neurotoxicity in immature offspring rats through regulation of AROM, ER-β, BDNF and p-CREB expression, while it has no influence on mature offspring animals.

Effects of in utero di-butyl phthalate and butyl benzyl phthalate exposure on offspring development and male reproduction of rat

The study was conducted to assess the effects of in utero di-butyl phthalate (DBP) and butyl benzyl phthalate (BBP) exposure during late gestation on offspring's development and reproductive system of male rats. Pregnant rats were treated orally with DBP (2, 10, 50 mg/kg), BBP (4, 20, 100 mg/kg), and diethylstilbestrol (DES) 6 μg/kg (positive control) from GD14 to parturition. A significant reduction in dams' body weight on GD21 in DBP-, BBP-, and DES-treated groups was observed. The gestation length was considerably elevated in the treated groups. Decline in male pups' body weight was significant at PND75 in DBP- (50 mg/kg), BBP- (20,100 mg/kg), and DES-treated groups. The weight of most of the reproductive organs and sperm quality parameters was impaired significantly in DBP- (50 mg/kg) and BBP- (100 mg/kg) treated groups. Further, a non-significant decline in testicular spermatid count and daily sperm production was also monitored in treated groups. A significant reduction in serum testosterone level in BBP (100 mg/kg), whereas the testicular activity of 17β-HSD was declined non-significantly in the treated groups with respect to control. The data suggests that DBP and BBP exposure during late gestation period might have adverse effects on offspring's development, spermatogenesis, and steroidogenesis in adult rats.

Association between phthalates and attention deficit disorder and learning disability in U.S. children, 6-15 years

OBJECTIVE

This study investigates the association between urinary phthalate metabolite levels and attention deficit disorder (ADD), learning disability (LD), and co-occurrence of ADD and LD in 6-15-year-old children.

METHODS

We used cross-sectional data from the National Health and Nutrition Examination Survey (NHANES, 2001-2004). Phthalate metabolites with ≥75% detection in urine samples were examined. The study population comprised 1493 children with parent-reported information on ADD or LD diagnosis and phthalate concentrations in urine. Phthalate concentrations were creatinine-adjusted and log10-transformed for analysis. All models controlled for child sex, age, race, household income, blood lead, and maternal smoking during pregnancy.

RESULTS

There were 112 ADD cases, 173 LD cases, and 56 ADD and LD cases in the sample. After adjusting for potential confounders, we found increased odds of ADD with increasing urinary concentration of di-2-ethylhexyl phthalates (OR: 2.1; 95% CI: 1.1, 3.9) and high molecular weight phthalates (OR: 2.7; 95% CI: 1.2, 6.1). In addition, dibutyl phthalates (OR: 3.3; 95% CI: 0.9, 12.7) and high molecular weight phthalates (OR: 3.7; 95% CI: 0.9, 14.8) were marginally associated with increased odds of co-occurring ADD and LD. We did not find associations for any phthalate and LD alone. We observed stronger associations between phthalates and ADD and both ADD and LD in girls than boys in some models.

CONCLUSIONS

We found cross-sectional evidence that certain phthalates are associated with increased odds of ADD and both ADD and LD. Further investigations with longitudinal data are needed to confirm these results.

Phthalates induce neurotoxicity affecting locomotor and thermotactic behaviors and AFD neurons through oxidative stress in Caenorhabditis elegans

Background

Phthalate esters are ubiquitous environmental contaminants and numerous organisms are thus exposed to various levels of phthalates in their natural habitat. Considering the critical, but limited, research on human neurobehavioral outcomes in association with phthalates exposure, we used the nematode Caenorhabditis elegans as an in vivo model to evaluate phthalates-induced neurotoxicity and the possible associated mechanisms.

Principal Findings

Exposure to phthalates (DEHP, DBP, and DIBP) at the examined concentrations induced behavioral defects, including changes in body bending, head thrashing, reversal frequency, and thermotaxis in C. elegans. Moreover, phthalates (DEHP, DBP, and DIBP) exposure caused toxicity, affecting the relative sizes of cell body fluorescent puncta, and relative intensities of cell bodies in AFD neurons. The mRNA levels of the majority of the genes (TTX-1, TAX-2, TAX-4, and CEH-14) that are required for the differentiation and function of AFD neurons were decreased upon DEHP exposure. Furthermore, phthalates (DEHP, DBP, and DIBP) exposure at the examined concentrations produced elevated intracellular reactive oxygen species (ROS) in C. elegans. Finally, pretreatment with the antioxidant ascorbic acid significantly lowered the intracellular ROS level, ameliorated the locomotor and thermotactic behavior defects, and protected the damage of AFD neurons by DEHP exposure.

Conclusions

Our study suggests that oxidative stress plays a critical role in the phthalate esters-induced neurotoxic effects in C. elegans.

Neurotoxicity of dibutyl phthalate in brain development following perinatal exposure: a study in rats

Dibutyl-phthalate (DBP) is a ubiquitous environmental contaminant. However, its neurotoxic effects on neonatal, immature or mature brains remain unclear. Here, we aimed to investigate the neurotoxicity of perinatal exposure of DBP on rodent offspring animals. Pregnant rats received intragastric DBP (500mg/kg body weight) daily from gestational day (GD) 6 to postnatal day (PND) 21. Animals in the control group received the same volume of edible corn oil. Brain sections or tissues from offspring rats on PND5, PND21 and PND60 were collected for analysis. Histological examination demonstrated that perinatal exposure of DBP resulted in hippocampal neuron loss and structural alternation in neonatal and immature offspring rats (PND5 and PND21), while no significant change was found in mature rats (PND60). DBP exposure induced cell apoptosis in hippocampal neurons of these neonatal and immature animals, as evidenced by the increased number of TUNEL-positive and Annexin V-propidium iodide (PI) positive cells and up-regulated caspase-3 activity. Moreover, DBP exposure decreased the expression of synaptophysin in the hippocampus and reduced both the slope and amplitude of field excitatory postsynaptic potentials (fEPSPs). DBP also impaired the spatial learning and memory of offspring rats. However, no significant difference in the susceptibility to DBP-induced neurotoxicity was found between male and female offspring rats. Our findings indicated that perinatal exposure of DBP could induce neurotoxicity in neonatal and immature offspring animals, but had no influence on mature animals after DBP withdrawal. These results may provide basic experimental evidence for better understanding the neurotoxic effects of DBP on neonatal, immature and mature brains.

Antiandrogenic effect of perinatal exposure to the endocrine disruptor di-(2-ethylhexyl) phthalate increases anxiety-like behavior in male rats during sexual maturation

Di-2-ethylhexyl phthalate (DEHP) is the most widely used phthalate to convey flexibility and transparency to plastic products made of polyvinyl chloride. It has been recognized as endocrine disruptor and associated with reproductive toxic effects. We examined the effects of perinatal exposure to DEHP on anxiety-like behavior, using the Elevated Plus Maze (EPM) test, in male and female rats at different stages of sexual development. Anxiety-like behavior was expressed as a) frequency of open arm entries over the total arm entries (% FEO); b) time spent in them compared with total time the animal stayed in the EPM (% TSO) and c) time spent in closed arms (TSC). Because DEHP has anti-androgenic action we also tested control and exposed immature male rats pretreated with testosterone. We found sex differences in behavior induced by DEHP; while male rats of 45 and 60 days of age showed a significant decrease in FEO and TSO percentages, as well as an increase in TSC, no changes were observed in anxiety-like behavior in perinatal DEHP exposed females at these ages of sexual maturation. In 60-day-old male rats, DEHP exposure produced a significant decrease in serum testosterone levels. Testosterone replacement was able to antagonize the adverse effects of DEHP exposure on LH, activating the negative feed-back mechanism of this steroid on reproductive axis, as well as increasing FEO and TSO percentages to similar values observed in the control group. These findings suggest that the anti-androgenic action of this chemical could be one possible mechanism underlie anxiogenic-like behavior produced by perinatal DEHP exposure in 60-day-old male rats.

Maternal prenatal urinary phthalate metabolite concentrations and child mental, psychomotor, and behavioral development at 3 years of age

BACKGROUND

Research suggests that prenatal phthalate exposures affect child executive function and behavior.

OBJECTIVE

We evaluated associations between phthalate metabolite concentrations in maternal prenatal urine and mental, motor, and behavioral development in children at 3 years of age.

METHODS

Mono-n-butyl phthalate (MnBP), monobenzyl phthalate (MBzP), monoisobutyl phthalate (MiBP), and four di-2-ethylhexyl phthalate metabolites were measured in a spot urine sample collected from 319 women during the third trimester. When children were 3 years of age, the Mental Development Index (MDI) and Psychomotor Development Index (PDI) were measured using the Bayley Scales of Infant Development II, and behavior problems were assessed by maternal report on the Child Behavior Checklist.

RESULTS

Child PDI scores decreased with increasing loge MnBP [estimated adjusted β-coefficient = -2.81; 95% confidence interval (CI): -4.63, -1.0] and loge MiBP (β = -2.28; 95% CI: -3.90, -0.67); odds of motor delay increased significantly [per loge MnBP: estimated adjusted odds ratio (OR) = 1.64; 95% CI: 1.10, 2.44; per loge MiBP: adjusted OR =1.82; 95% CI: 1.24, 2.66]. In girls, MDI scores decreased with increasing loge MnBP (β = -2.67; 95% CI: -4.70, -0.65); the child sex difference in odds of mental delay was significant (p = 0.037). The ORs for clinically withdrawn behavior were 2.23 (95% CI: 1.27, 3.92) and 1.57 (95% CI: 1.07, 2.31) per loge unit increase in MnBP and MBzP, respectively; for clinically internalizing behaviors, the OR was 1.43 (95% CI: 1.01, 1.90) per loge unit increase in MBzP. Significant child sex differences were seen in associations between MnBP and MBzP and behaviors in internalizing domains (p < 0.05).

CONCLUSION

Certain prenatal phthalate exposures may decrease child mental and motor development and increase internalizing behaviors.

Prenatal exposure to bisphenol A and phthalates and infant neurobehavior

OBJECTIVE

To examine the association of prenatal exposure to bisphenol A and select common phthalates with infant neurobehavior measured at 5 weeks.

METHODS

We compared the concentration of maternal urinary metabolites of bisphenol A and phthalates at two distinct time points in pregnancy (16w, 26w) with scores on the NICU Network Neurobehavioral Scale (NNNS) at 5 weeks of age in a cohort of 350 mother/infant pairs.

RESULTS

Prenatal exposure to BPA was not significantly associated with neurobehavioral outcomes at 5 weeks. Significant associations between prenatal exposure to measured phthalates and infant neurobehavioral outcomes differed by type of phthalate and were only seen with exposure measured at 26 weeks. Higher total di-butyl phthalate (DBP) metabolites at 26w were associated with improved behavioral organization evidenced by decreased arousal (p=.04), increased self-regulation (p=.052), and decreased handling (p=.02). In males, higher total di-2-ethylhexyl phthalate (DEHP) metabolites at 26w were associated with more nonoptimal reflexes (p=.02).

CONCLUSION

The association between prenatal phthalate exposure and infant neurobehavior differed by type of phthalate and was evident only with exposure measured at 26w. Prenatal exposure to DBP was associated with improved behavioral organization in 5-week-old infants. Prenatal exposure to DEHP was associated with nonoptimal reflexes in male infants. There was no evidence of an association between prenatal BPA exposure and infant neurobehavior.